A wheel type working vehicle, in which a driving unit, in which an engine, and a mechanical-hydraulic transmission (hereinafter, simply called a transmission) capable of selectively switching a mechanical driving force and a hydraulic driving force by switching a clutch in accordance with traveling ranges of a plurality of gears are integrally connected without interposing a torque converter, is placed on a lower part of a chassis frame, is proposed, and the one is disclosed in, for example, patent document 1. FIG. 5 and FIG. 6 is a plane view of a base carrier of a wheel type working vehicle disclosed in patent document 1, and a schematic view of its power train. Here, patent document 1 is Japanese Patent Laid-open No. 2002-362174, and the wheel type working vehicle is disclosed especially on pages 5 to 6, FIG. 1, and FIG. 3.
In FIG. 5 and FIG. 6, an engine 80 is placed at a right side of a chassis frame 81 with its output shaft axis C—C facing in a lateral direction of the vehicle. A transmission 82 is placed on a lower part in the chassis frame 81 in a direction of an output shaft 81a of the engine 80. The output shaft 80a of the engine 80 is integrally connected to the transmission 82. A front and rear wheel driving output shaft 98 having a rear output shaft 98a and a front output shaft 98b is placed in a longitudinal direction of the vehicle at a left side of the transmission 82. The rear output shaft 98a and the front output shaft 98b are connected to a rear and a front wheel axles 85a and 85b via propeller shafts 95a and 95b, and differential devices 86a and 86b, respectively.
The transmission 82 includes a first input shaft 87 connected to the output shaft of the engine 80, a first intermediate shaft 88, and an output shaft 89 (shown by an output shaft axis E—E in FIG. 5) to be in parallel. The shafts 87, 88 and 89 are provided respectively with a deceleration gear train 90 and speed change gear clutches 92, 93 and 94. Power of the engine 80 is mechanically shifted and transmitted to the output shaft 89 via the deceleration gear train 90 and each of the speed change gear clutches 92, 93 and 94. The transmission 82 includes a second input shaft 96, and a second intermediate shaft 97. A hydraulic motor 84, which receives discharge oil of a hydraulic pump 83 connected to an opposite side from the engine 80 in the first input shaft 87 and is rotationally driven via a control valve (not shown), is connected to the second input shaft 96. The second input shaft 96 and the second intermediate shaft 97 are provided with a deceleration gear train 99 and a speed change gear clutch 91. A hydraulic driving force of the hydraulic motor 84 is transmitted to the output shaft 89 via the deceleration gear train 99 and the speed change gear clutch 91.
A shaft 101 provided with a bevel gear 102 is connected to the output shaft 89, and the bevel gear 102 is meshed with a bevel gear 103 provided at the rear output shaft 98a. An output power of the output shaft 89 of the transmission 82 is transmitted to the rear output shaft 98a via the bevel gears 102 and 103. The rear output shaft 98a is selectively connected to the front output shaft 98b via a mechanical clutch mechanism 104.
According to the above-described constitution, when only the speed change gear clutch 91 is engaged, the speed is in a low-speed traveling range of a first speed gear, and the driving force of the hydraulic motor 84 is outputted from the output shaft 89 via the deceleration gear train 99 and the second intermediate shaft 97. When the speed change gear clutches 92, 93, and 94 are individually engaged respectively, the speed is in a high-speed traveling range of the second, third and fourth speed gear, and the driving force of the engine 80 is outputted from the output shaft 89 via the deceleration gear train 90 and the first intermediate shaft 88. Namely, the mechanical driving force and the hydraulic driving force are constituted so as to be outputted from the common output shaft 89.
In the transmission disclosed in patent document 1, the mechanical driving force and the hydraulic driving force are outputted to the front and rear wheel driving output shaft 98 via the common output shaft 89 and the bevel gears 102 and 103. Thus, in order to stand driving at a low-speed with high torque at the time of hydraulic driving, the output shaft 89 and the bevel gears 102 and 103 have to transmit a hydraulic driving power with a large torque capacity, and therefore it becomes necessary to increase the output shaft 89 and the bevel gears 102 and 103 in size, thus causing the problem of the entire transmission becoming large.